1. Field of the Invention
This invention relates to a thin reinforced nonwoven fabric, made from a compressed web of crimped fiber and a reinforcing scrim, that bulks when exposed to heat or flame and that is useful as a component for fire blocking mattresses, upholstery, and the like. This invention further relates to a fire-blocked article incorporating this fabric. This invention also relates to processes for making this reinforced nonwoven fabric and incorporating the fabric into an article.
2. Description of Related Art
The State of California has led the drive to regulate and reduce the flammability of mattresses and mattress sets in an attempt to reduce the number of lives lost in household, hotel, and institutional fires. In particular, the Bureau of Home Furnishings and Thermal Insulation of the Department of Consumer Affairs of the State of California issued Technical Bulletin 603 “Requirements and Test Procedure for Resistance of a Residential Mattress/Box Spring Set to a Large Open-Flame” to quantify the flammability performance of mattress sets. In many cases, mattress makers want to include a layer of fire blocking, however, they do not want that additional layer to detract from the existing aesthetics of their mattresses. Strong thin fabrics, such as a combination of staple fibers and a thin reinforcing scrim fabric, are therefore desired in many instances because they are durable and also are not likely to be objectionable in the intended use.
Various methods are known in the art for combining staple fibers and scrim fabrics that lock the staple fibers in place. One such process is hydro-entangling, also known in various publications as hydrolacing, spunlacing, and water-jet treatments, where high pressure water jets impact the staple fibers and drive them into the scrim, consolidating the fiber and scrim together. Nonwoven sheets made by this process mechanically entangle the staple fibers either with themselves or with the scrim or both, limiting the ability of the fabric to bulk when heated or exposed to flame. The following patents are representative of nonwoven fabrics made primarily by the hydro-entangling process. PCT Publication WO 98/42905 discloses a multilayer textile material consisting of a complex textile grid embedded inside a textile structure consisting of nonwoven laps arranged on either side of the grid, the laps entangled with each other and the grid by the force of hydro-entangling. U.S. Pat. No. 4,840,838 to Wyss discloses a high temperature filter felt of a scrim and batt of fibers entangled into that scrim. U.S. Pat. No. 6,596,658 to Putnam et al discloses a laminated fabric having a three dimensional image, the fabric formed from a lightweight layer of heat-resistant fibers and a heavyweight layer bonded together via hydro-entanglement.
Another process known in the art for combining staple fibers and scrim fabrics is by needlepunching. In this process, barbed needles grab the staple fibers and drive them into the scrim, or into the internal fiber batting, locking together the structure. Again, nonwoven sheets made by this process have their staple fibers mechanically entangled either with themselves or with the scrim, limiting the ability of the fabric to bulk when heated or exposed to flame. Some products made by needlepunching can be made by hydro-entangling, or vice versa, since both products require the entangling of the fibers with and to the scrim and other fibers in the fabrics. The following patents are representative of nonwoven fabrics made primarily by the needlepunching process. U.S. Pat. No. 4,743,495 to Lilani et al. discloses a nonwoven fire blocking seat fabric comprising at least two felted plies comprising aramid fibers and phenolic fibers that are united together with a stabilized woven scrim. U.S. Pat. No. 5,691,036 to Lin et al. discloses a cushioning material having at least two layers of unwoven temperature-resistant staple fibers with layers of reinforcing scrim between the layers, wherein the entire structure is needlepunched for integrity and one face is embossed with a pattern. U.S. Pat. No. 3,819,465 to Parsons et al. discloses a textile construction having a resilient textured surface formed by needlepunching nonwoven fibers into a layer of plastic grid material. The grid is then caused to retract and cause the nonwoven fibers to arch out of the plane of the batt, forming the textured surface. U.S. Pat. No. 5,578,368 to Forsten et al. discloses a fire-resistant material useful in upholstered furniture and mattress tops, comprising a fiberfill batt and a layer of fire-resistant aramid fiber contacting at least one side of the fiberfill batt. Another fire blocking material is made by entangling flame resistant fibers to and with a scrim via hydro-entangling, needlepunching, and/or chemical means, is disclosed in United States Patent Application 2002/0098753 to Latham et al. Such materials are useful for fire blocking aircraft seats.
Still another process known in the art for combining staple fibers and scrim fabric is by adhesive lamination or the addition of binders. In this process, a binder or adhesive is used to either adhere or bind layers or individual fibers together. The following patents are representative of nonwoven fabrics made by this process. U.S. Pat. Nos. 6,579,396 and 6,383,623 to Erb disclose a very low-density insulating material having non-thermoplastic fibers that are bound by a flammable thermoplastic binder. European Patent EP 622 332 to Yamaguchi et al. discloses a heat resistant and flame-retardant cushioning structure comprising a matrix fiber of a bulky nonwoven web of crimped non-elastic staple fiber, a crimped flame-retardant fiber exhibiting residual weight of at least 35% as tested by a glowing test method, and a thermoplastic elastic fiber, with at least some of the intersecting points between the matrix fiber and the flame-retardant fiber with thermoplastic fiber being fusion bonded. The matrix fiber is preferably polyester or aramid fiber, but preferably the polyester contains a flame retardant compound and the preferred aramid fiber is a meta-aramid fiber. The flame-retardant fiber is preferably pre-oxidized acrylonitrile polymer fiber, but can be carbon fiber, crosslinked phenolic resin fiber, or polybenizimidazole fiber. The preferred thermoplastic elastomer fiber is a sheath/core composite fiber made of thermoplastic elastomer and a non-elastic polyester. The Erb and Yamaguchi patents both use the binder to maintain the nonwoven in a lofted or bulked form so that it will have resiliency. U.S. Pat. No. 5,470,648 to Pearlman et al. discloses a three-layered composite fabric for use a carpet backing, the composite fabric made from two layers of entangled nylon filaments adhesively attached to a fiberglass scrim. This fabric has the same problem hydro-entangled or needlepunched fabrics have, that is, because the fibers are mechanically entangled together they lose their ability to bulk when heated or exposed to flame.
What is needed therefore, is a reinforced nonwoven fabric that provides flame protection but is lightweight and thin during normal use but then bulks when subjected to high heat or flame.